1. Field of the Invention
The present invention relates to a vehicle collision sensing system, which senses, for example, a pressure in an interior space of a door of a vehicle and determines collision of the vehicle based on the sensed pressure.
2. Description of Related Art
One previously proposed way of activating an occupant protective device is use of a pressure sensor, which serves as a collision sensing means for sensing a collision of the vehicle (see, for example, Japanese Unexamined Patent Publication No. H02-249740). For example, Japanese Unexamined Patent Publication No. H02-249740 recites a system that includes an airtight air tank, which is arranged in an interior space of a door of a vehicle, and a pressure sensor, which senses a pressure in the air tank. In this system, when the pressure in the air tank sensed by the pressure sensor becomes equal to or greater than a predetermined threshold value, it is determined that a collision of the vehicle has occurred, and a protective device, such as an air bag, is activated.
However, a receiving space for receiving the air tank in the interior space of the vehicle door needs to be provided. Therefore, the limitations on the designing of the vehicle door and the air tank are increased. Furthermore, the provision of the air tank leads to an increase in the manufacturing costs. In view of this, it is conceivable to eliminate the air tank and directly measure the pressure in the interior space of the vehicle door with the pressure sensor to sense the collision of the vehicle. That is, the collision may be determined by comparing the pressure in the interior space of the door of the vehicle door with the predetermined threshold value.
However, the pressure in the interior space of the vehicle door substantially changes when the atmospheric pressure substantially changes due to a substantial change in an altitude and/or weather of a current location of the vehicle. When the collision of the vehicle is determined by comparing the pressure in the interior space of the vehicle door with the predetermined threshold value, there is a possibility that the collision of the vehicle cannot be reliably sensed. This is also true in the case where the air tank is provided in the vehicle door.